This invention relates to a weft picking device for an air jet type shuttleless weaving loom, including a plurality of air guide members forming an air guide channel therethrough so as to carry out weft picking by guiding and carrying a weft yarn inserted by a weft inserting nozzle or main nozzle under the influence of an air jet, and more particularly to the a weft picking device which is provided with an auxiliary nozzle for assisting the weft picking operation along the air guide channel.
In connection with most air jet type weaving looms, conventionally used weft picking devices and particularly weft carrying devices thereof, are divided broadly into two kinds.
The first kind of device is disclosed in Japanese Patent Provisional Publication No. 47-7576, in which a plurality of auxiliary nozzles, each having a nozzle opening, is provided at a side of an air guide channel through which a weft yarn passes to be picked, the air ejection line from the nozzle opening being directed so as to be substantially parallel with the moving direction of the picked weft yarn. Additionally, in such a device, the following measures are necessary and adapted in order to prevent the picked weft yarn from deviating from a scheduled line: (1) an air guide member of U-shape having a groove which is closed in three directions is disposed at a plurality of locations as disclosed in the above-mentioned Japanese Patent Provisional Publication; (2) such a groove is formed at the dent section of a reed; and (3) the scheduled line for weft picking is so directed as to positively introduce the picked weft yarn into the above-mentioned groove. With such a weft inserting device, at about the time when the leading end of a picked weft yarn injected from a main nozzle under the action of an air jet ejected from the main nozzle reaches the front-most auxiliary nozzle, an auxiliary air jet is ejected from an auxiliary nozzle to blow up the leading end of the picked weft yarn in the direction of weft picking. This operation is carried out in turn by succeeding auxiliary nozzles to achieve weft picking.
As will be understood, the method of weft picking of such a weft picking device is suitable for a weaving loom for weaving a wide fabric. However, this method for weft insertion has encountered difficulties in which the air jet from the main nozzle is spread immediately after air ejection from the auxiliary nozzle, and accordingly the air jet from the main nozzle is almost not used to carry the weft yarn along the air guide channel, wasting expensive pressurized air.
The second kind of device for weft picking is provided with an air guide channel which is constructed with air guide members which are aligned relatively close to each other. Each air guide member is formed into a generally circular shape, leaving an air guide opening which is tapered in the direction of weft insertion. With this arrangement, air ejected from a main nozzle advances within the air guide channel receiving a converging effect from the tapered surface of the air guide opening, even after the air ejected from the main nozzle completes the drawing and dispatching actions to the weft yarn. It will be understood that the weft yarn injected from the main nozzle is carried by the action of the air stream produced as described above.
According to the method of the above-mentioned second kind of weft picking device, although the ejected air from the main nozzle is effectively used for carrying the weft yarn through the air guide channel and accordingly operation and equipment costs are reduced, it is unavoidable that the advancing air flow stream gradually leaks out of each clearance between the adjacent air guide members and out of a slit of the air guide member through which slit a weft yarn escapes. Hence, this weft picking device has encountered the drawback in which the intensity of the air stream becomes insufficient at a side of the loom, opposite to a side provided with the main nozzle.
In order to overcome this drawback, it will be appreciated that an auxiliary nozzle is installed to compensate for the above-mentioned air leaks and to intensify the air stream. For this purpose, it is necessary not to disturb the the main air stream from the main nozzle by the air jet ejected from the auxiliary nozzle, which has been already disclosed in Japanese Patent Provisional Publication Nos. 49-47661 and 52-49361. In the weft insertion devices shown in these publications, the auxiliary nozzles are formed as parts of the air guide members. Accordingly, these auxiliary nozzles are constructed with a plurality of circular or slit-like nozzle openings which are formed immediately outside and in the vicinity of the air guide opening of the air guide member, which nozzle openings are located symmetrically with each other relative to a point. These nozzle openings are directed to a point which lies downstream of the nozzle openings in the scheduled weft picking path, so that a high speed air jet from the nozzle openings of the auxiliary nozzles are added uniformly from around the air guide channel to the air stream in the air guide channel. Since the nozzle openings of the auxiliary nozzles are symmetrically are located relative to a point, the shape of the entire body necessarily becomes annular. Furthermore, the auxiliary nozzle must act with the air guide members so as to push aside the warp yarns to enter the shed and then withdraw from the shed. In this regard, th outer shape of the auxiliary nozzle should be the same as that of the air guide member. It will be understood from this that the auxiliary nozzle is formed as part of the air guide member.
Now, it is to be noted that the thickness of the air guide member is normally limited approximately to 2 to 3 mm, and accordingly when a flow pass for ejection air is formed inside of the air guide member and air introduction paths are branched off from the flow pass to air ejection nozzle openings, the sectional areas of these paths and the lengths of the air introduction paths are considerably limited. This unavoidably results in differences in air ejection speed, air ejection amount, and air ejection direction, among a plurality of nozzle openings. As a result, the air stream of the air guide channel is disturbed by the air ejections from the nozzle openings formed at the air guide member, by which an effective weft picking becomes impossible.
Hence, the above-mentioned second kind of device for weft picking seems undesirable from the standpoint of preventing the air stream in the air guide channel from being disturbed, i.e., directing always the air stream line from the nozzles openings of auxiliary nozzle along the weft picking path. In view of the above, the purpose of this invention was to achieve a desirable weft picking by employing a simple auxiliary nozzle which is similar to that of the above-mentioned first device for weft picking, in which the simple auxiliary air stream from the auxiliary nozzle is added angularly to a main air stream in the air guide channel so as to guide and assist the main air stream, and further to immediately recover the main air stream into a normal state under the action of the auxiliary air stream which repeats the main air stream's reflection on the opposite inner surfaces of the air guide members, if the main air stream is once disturbed.